Every March I have the pleasure of speaking to students studying web development and design at ANU about images and image credibility. One of these students sent me this photograph, a tragi-comic image that makes one wince and laugh at the same time.
As an image credibilitist, I was intrigued. Was it real? It’s not hard to imagine a photographer with the good fortune to be photographing someone doing a bike trick that went horribly wrong right in front of the camera.
I examined it closely. Everything seemed to look correct from the shadows on the ground to lines that resembled impact waves on the man’s face. Further, it put me in mind of a similar accident that happened to one of my brothers – the loss of a front wheel off the bike fork leading to a complete wipe-out.
Despite this, I was yet to be convinced. Was the scene a bit too ‘lined up’? Was the escaping wheel too conveniently positioned square to the camera?
As a stared at the photo and the quite distinctive shadows on the concrete, I thought about the famous Australian photographer Frank Hurley and a particular Antarctic photograph I wrote about in some previous research.
‘Ocean Camp, Weddell Sea’ Frank Hurley, 1915 
Hurley took this extraordinary photo during the Shackleton Imperial Trans-Antarctic Expedition (1914-1917), recording the harsh conditions of the Weddell Sea ice shelf. At the same time it also wonderfully records the beautiful oddity of penguins and the indomitability of life in the face of severe adversity.
However, it is a composite image. It is easy to see if we look to the shadows. The dark sled dogs and sled in the mid-ground cast long shadow leading right and down, indicating that light source (the sun) was behind and to the left. Simultaneously, the foreground penguins cast no shadow, in fact they seemingly lit from the front. Since it would defy the laws of physics for both of these things to be true at the same moment, the image has to be composited. 
Remembering that, and having recently read an article in which a leader in my field, Professor Hany Farid at Dartmouth College, commented about the importance of shadows as a key to ascertaining the veracity of an image , I looked more closely at the shadows in the bike accident photo. Well, they looked as they should. So that wouldn’t tell me anything. Hmmm, or would it?
I imported the image into Powerpoint and superimposed lines connecting features of the main objects in the image to their shadow points on the pavement. In short order, I had my answer. I won’t keep you in suspense any longer. My assessment of the Falling Bike Guy is that it was not only composited, but staged as well. The photograph is not a photograph, it is photoART.
The lines in this image show the directionality of the light source. Clearly the escaping wheel was lit by sunlight coming from the top right, and the falling guy is lit by sunlight coming from the top left. This indicates that the sun was in a different position at the time of each photograph. The middle element is more confusing. At the moment, I have tentatively suggested that the light source for the upended Schwinn comes from two slightly different positions of the sun (perhaps from being held up from first one side then the other?), but I may explore this further. At the very least, the average light source position is different from both the escaping wheel and the falling guy.
Logically, if the three main elements of the image were taken at different times, then the falling man is not involved in an accident, but instead is staging himself to appear as though he was. With either the assistance of a friend, or with a camera on a tripod with a remote trigger, timed shutter, or bracket photography (or a combination thereof), our man collected several photographs, then composited them in Photoshop or a similar photo editor.
In fact, if one visits ‘Gratisography’ , the site from which this image was sourced by my student, it is a simple matter to discover that the man in this image is in fact Ryan Mcguire himself, the founder of Gratisography.
So next time you find yourself wondering whether a photograph is real, take a closer look. You may find your answer lurking in the shadows.
 Hurley, Frank (2015) Ocean Camp, Weddell Sea. In the collection of the National Library of Australia Ref: NLA.pic.an24039566-v
 Hurley later admitted to the compositing, and explained that he couldn’t portray the entire feel of the experience without bringing different things together into one image. I believe I learned this in a book by Helen Ennis of ANU on Hurley’s Antarctic photography. (quote/reference to be added soon)
 Eric Kee, James O’Brien, and Hany Farid. Exposing Photo Manipulation with Inconsistent Shadows. ACM Transactions on Graphics, 32(4):28:1–12, 2013.